Internet DRAFT - draft-ietf-opsawg-capwap-alt-tunnel
draft-ietf-opsawg-capwap-alt-tunnel
Opsawg Working Group R. Zhang
Internet-Draft China Telecom
Intended status: Experimental R. Pazhyannur
Expires: August 2, 2018 S. Gundavelli
Cisco
Z. Cao
H. Deng
Z. Du
Huawei
January 29, 2018
Alternate Tunnel Encapsulation for Data Frames in CAPWAP
draft-ietf-opsawg-capwap-alt-tunnel-12
Abstract
Control and Provisioning of Wireless Access Points (CAPWAP) defines a
specification to encapsulate a station's data frames between the
Wireless Transmission Point (WTP) and Access Controller (AC).
Specifically, the station's IEEE 802.11 data frames can be either
locally bridged or tunneled to the AC. When tunneled, a CAPWAP data
channel is used for tunneling. In many deployments encapsulating
data frames to an entity other than the AC (for example to an Access
Router (AR)) is desirable. Furthermore, it may also be desirable to
use different tunnel encapsulation modes between the WTP and the
Access Router. This document defines extension to CAPWAP protocol
for supporting this capability and refers to it as alternate tunnel
encapsulation. The alternate tunnel encapsulation allows 1) the WTP
to tunnel non-management data frames to an endpoint different from
the AC and 2) the WTP to tunnel using one of many known encapsulation
types such as IP-IP, IP-GRE, CAPWAP. The WTP may advertise support
for alternate tunnel encapsulation during the discovery and join
process and AC may select one of the supported alternate tunnel
encapsulation types while configuring the WTP.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 2, 2018.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 7
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.3. History of the document . . . . . . . . . . . . . . . . . 8
2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 8
3. CAPWAP Protocol Message Elements Extensions . . . . . . . . . 11
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12
4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13
4.1. CAPWAP based Alternate Tunnel . . . . . . . . . . . . . . 13
4.2. PMIPv6 based Alternate Tunnel . . . . . . . . . . . . . . 14
4.3. GRE based Alternate Tunnel . . . . . . . . . . . . . . . 15
5. Alternate Tunnel Information Elements . . . . . . . . . . . . 15
5.1. Access Router Information Elements . . . . . . . . . . . 15
5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16
5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 16
5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17
5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19
5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20
5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22
5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
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9.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
Service Providers are deploying very large Wi-Fi network containing
hundreds of thousands of Access Points (APs), which are referred to
as Wireless Transmission Points (WTPs) in Control and Provisioning of
Wireless Access Points (CAPWAP) terminology [RFC5415]. These
networks are designed to carry traffic generated from mobile users.
The volume in mobile user traffic is already very large and expected
to continue growing rapidly. As a result, operators are looking for
scalable solutions that can meet the increasing demand. The
scalability requirement can be met by splitting the control/
management plane from the data plane. This enables the data plane to
scale independent of the control/management plane. This
specification provides a way to enable such separation.
CAPWAP ([RFC5415], [RFC5416]) defines a tunnel mode that describes
how the WTP handles the data plane (user traffic). The following
types are defined:
o Local Bridging: All data frames are locally bridged.
o 802.3 Tunnel: All data frames are tunneled to the Access
Controller (AC) in 802.3 format.
o 802.11 Tunnel: All data frames are tunneled to the AC in 802.11
format.
Figure 1 describes a system with Local Bridging. The AC is in a
centralized location. The data plane is locally bridged by the WTPs
leading to a system with centralized control plane with distributed
data plane. This system has two benefits: 1) reduces the scale
requirement on data traffic handling capability of the AC and 2)
leads to more efficient/optimal routing of data traffic while
maintaining centralized control/management.
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Locally Bridged
+-----+ Data Frames +----------------+
| WTP |===============| Access Router |
+-----+ +----------------+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt traffic +----------+
//
+-----+ +----------------+
| WTP |============== | Access Router |
+-----+ +----------------+
Locally Bridged
Data Frames
Figure 1: Centralized Control with Distributed Data
The AC handles control of WTPs. In addition, the AC also handles the
IEEE 802.11 management traffic to/from the stations. There is CAPWAP
Control and Data Channel between the WTP and the AC. Note that even
though there is no user traffic transported between the WTP and AC,
there is still a CAPWAP Data Channel. The CAPWAP Data Channel
carries the IEEE 802.11 management traffic (like IEEE 802.11 Action
Frames).
Figure 2 shows a system where the tunnel mode is configured to tunnel
data frames between the WTP and the AC either using 802.3 Tunnel or
802.11 Tunnel configurations. Operators deploy this configuration
when they need to tunnel the user traffic. The tunneling requirement
may be driven by the need to apply policy at the AC. This
requirement could be met in the locally bridged system (Figure 1) if
the Access Router (AR) implemented the required policy. However, in
many deployments the operator managing the WTP is different than the
operator managing the Access Router. When the operators are
different, the policy has to be enforced in a tunnel termination
point in the WTP operator's network.
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+-----+
| WTP |
+-----+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt traffic | |
// Data Frames +----------+
//
+-----+
| WTP |
+-----+
Figure 2: Centralized Control and Centralized Data
The key difference with the locally bridged system is that the data
frames are tunneled to the AC instead of being locally bridged.
There are two shortcomings with the system in Figure 2. 1) They do
not allow the WTP to tunnel data frames to an endpoint different from
the AC and 2) They do not allow the WTP to tunnel data frames using
any encapsulation other than CAPWAP (as specified in Section 4.4.2 of
[RFC5415]).
Figure 3 shows a system where the WTP tunnels data frames to an
alternate entity different from the AC. The WTP also uses an
alternate tunnel encapsulation such as L2TP, L2TPv3, IP-in-IP, IP/
GRE, etc. This enables 1) independent scaling of data plane and 2)
leveraging of commonly used tunnel encapsulations such as L2TP, GRE,
etc.
Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.)
_________
+-----+ ( ) +-----------------+
| WTP |======+Internet +==============|Access Router(AR)|
+-----+ (_________) +-----------------+
\\ ________ CAPWAP Control
\\ ( ) Channel +--------+
++=+Internet+========================| AC |
// (________)CAPWAP Data Channel: +--------+
// IEEE 802.11 Mgmt traffic
// _________
+-----+ ( ) +----------------+
| WTP |====+Internet +================| Access Router |
+-----+ (_________) +----------------+
Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.)
Figure 3: Centralized Control with Alternate Tunnel for Data
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The WTP may support widely used encapsulation types such as L2TP,
L2TPv3, IP-in-IP, IP/GRE, etc. The WTP advertises the different
alternate tunnel encapsulation types it can support. The AC
configures one of the advertised types. As shown in the figure there
is a CAPWAP control and data channel between the WTP and AC. The
CAPWAP data channel carries the stations' management traffic as in
the case of the locally bridged system. The main reason to maintain
a CAPWAP data channel is to maintain similarity with the locally
bridged system. The WTP maintains three tunnels: CAPWAP Control,
CAPWAP Data, and another alternate tunnel for the data frames. The
data frames are transported by an alternate tunnel between the WTP
and a tunnel termination point such as an Access Router. This
specification describes how the alternate tunnel can be established.
The specification defines message elements for the WTP to advertise
support for alternate tunnel encapsulation, for the AC to configure
alternate tunnel encapsulation, and for the WTP to report failure of
the alternate tunnel.
The alternate tunnel encapsulation also supports the third-party WLAN
service provider scenario (i.e. Virtual Network Operator, VNO).
Under this scenario, the WLAN provider owns the WTP and AC resources,
while the VNOs can rent the WTP resources from the WLAN provider for
network access. The AC belonging to the WLAN service provider
manages the WTPs in the centralized mode.
As shown in Figure 4, VNO 1&2 don't possess the network access
resources, however they provide services by acquiring resources from
the WLAN provider. Since a WTP is capable of supporting up to 16
Service Set Identifiers (SSIDs), the WLAN provider may provide
network access service for different providers with different SSIDs.
For example, SSID1 is advertised by the WTP for VNO1; while SSID2 is
advertised by the WTP for VNO2. Therefore the data traffic from the
user can be directly steered to the corresponding access router of
the VNO who owns that user. As shown in Figure 4, AC can notify
multiple AR addresses for load balancing or redundancy.
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+----+
| AC |
+--+-+
CAPWAP-CTL |
+-----------------+
| CAPWAP-DATA: IEEE 802.11 Mgmt traffic
|
WLAN Provider| VNO 1
+-----+ CAPWAP-DATA (SSID1) +---------------+
SSID1 | WTP +--------------------------|Access Router 1|
SSID2 +--+-++ +---------------+
| |
| | VNO 1
| | GRE-DATA (SSID1) +---------------+
| +---------------------------|Access Router 2|
| +---------------+
|
| VNO 2
| CAPWAP-DATA (SSID2) +---------------+
+-----------------------------|Access Router 3|
+---------------+
Figure 4: Third-party WLAN Service Provider
1.1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Terminology
Station (STA): A device that contains an IEEE 802.11 conformant
medium access control (MAC) and physical layer (PHY) interface to the
wireless medium (WM).
Access Controller (AC): The network entity that provides WTP access
to the network infrastructure in the data plane, control plane,
management plane, or a combination therein.
Access Router (AR): A specialized router usually residing at the edge
or boundary of a network. This router ensures the connectivity of
its network with external networks, a wide area network or the
Internet.
Wireless Termination Point (WTP): The physical or network entity that
contains an RF antenna and wireless Physical Layer (PHY) to transmit
and receive station traffic for wireless access networks.
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CAPWAP Control Channel: A bi-directional flow defined by the AC IP
Address, WTP IP Address, AC control port, WTP control port, and the
transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Control
packets are sent and received.
CAPWAP Data Channel: A bi-directional flow defined by the AC IP
Address, WTP IP Address, AC data port, WTP data port, and the
transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Data
packets are sent and received. In certain WTP modes, the CAPWAP Data
Channel only transports IEEE 802.11 management frames and not the
data plane (user traffic).
1.3. History of the document
This document was started to accommodate Service Providers' need of a
more flexible deployment mode with alternative tunnels [RFC7494].
Experiments and tests have been done for this alt-tunnel network
infrastructure. However important, the deployment of relevant
technology is yet to complete. This experimental document is
intended to serve as an archival record for any future work as to the
operational and deployment requirements.
2. Alternate Tunnel Encapsulation Overview
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+-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request [ Supported Alternate |
| Tunnel Encapsulations ] |
|---------------------------------------->|
| |
|Join Response |
|<----------------------------------------|
| |
|IEEE 802.11 WLAN Configuration Request [ |
| IEEE 802.11 Add WLAN, |
| Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) |
| ] |
|<----------------------------------------|
| |
| |
+-+-+-+-+-+-+ |
| Setup | |
| Alternate | |
| Tunnel | |
+-+-+-+-+-+-+ |
|IEEE 802.11 WLAN Configuration Response |
|[ Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) ] |
|---------------------------------------->|
| |
| |
+-+-+-+-+-+-+ |
| Tunnel | |
| Failure | |
+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(report failure (AR address(es))) |
|---------------------------------------->|
| |
+-+-+-+-+-+-+-+ |
| Tunnel | |
| Established | |
+-+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(report clearing failure) |
|---------------------------------------->|
| |
Figure 5: Setup of Alternate Tunnel
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The above example describes how the alternate tunnel encapsulation
may be established. When the WTP joins the AC, it should indicate
its alternate tunnel encapsulation capability. The AC determines
whether an alternate tunnel configuration is required. If an
appropriate alternate tunnel type is selected, then the AC provides
the alternate tunnel encapsulation message element containing the
tunnel type and a tunnel-specific information element. The tunnel-
specific information element, for example, may contain information
like the IP address of the tunnel termination point. The WTP sets up
the alternate tunnel using the alternate tunnel encapsulation message
element.
Since AC can configure a WTP with more than one AR available for the
WTP to establish the data tunnel(s) for user traffic, it may be
useful for the WTP to communicate the selected AR. To enable this,
the IEEE 802.11 WLAN Configuration Response may carry the alternate
tunnel encapsulation message element containing the AR list element
corresponding to the selected AR as shown in Figure 5.
On detecting a tunnel failure, WTP SHALL forward data frames to the
AC and discard the frames. In addition, WTP may dissociate existing
clients and refuse association requests from new clients. Depending
on the implementation and deployment scenario, the AC may choose to
reconfigure the WLAN (on the WTP) to a local bridging mode or to
tunnel frames to the AC. When the WTP detects an alternate tunnel
failure, the WTP informs the AC using a message element, WTP
Alternate Tunnel Fail Indication (defined in this specification). It
MAY be carried in the WTP Event Request message which is defined in
[RFC5415].
The WTP also needs to notify the AC of which AR(s) are unavailable.
Particularly, in the VNO scenario, the AC of the WLAN service
provider needs to maintain the association of the AR addresses of the
VNOs and SSIDs, and provide this information to the WTP for the
purpose of load balancing or master-slave mode.
The message element has a status field that indicates whether the
message denotes reporting a failure or the clearing of the previously
reported failure.
For the case where AC is unreachable but the tunnel end point is
still reachable, the WTP behavior is up to the implementation. For
example, the WTP could either choose to tear down the alternate
tunnel or let the existing user's traffic continue to be tunneled.
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3. CAPWAP Protocol Message Elements Extensions
3.1. Supported Alternate Tunnel Encapsulations
This message element is sent by a WTP to communicate its capability
to support alternate tunnel encapsulations. The message element
contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type 1 | Tunnel-Type 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Tunnel-Type N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Supported Alternate Tunnel Encapsulations
o Type: <IANA-1> for Supported Alternate Tunnel Encapsulations
o Length: The length in bytes, two bytes for each Alternative tunnel
type that is included
o Tunnel-Type: This is identified by value defined in Section 3.2.
There may be one or more Tunnel-Types as shows in Figure 6.
3.2. Alternate Tunnel Encapsulations Type
This message element can be sent by the AC. This message element
allows the AC to select the alternate tunnel encapsulation. This
message element may be provided along with the IEEE 802.11 Add WLAN
message element. When the message element is present, the following
fields of the IEEE 802.11 Add WLAN element SHALL be set as follows:
MAC mode is set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local
Bridging). Besides, the message element can also be sent by the WTP
to communicate the selected AR(s).
The message element contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info Element
+-+-+-+-+-+-+-+-+-+
Figure 7: Alternate Tunnel Encapsulations Type
o Type: <IANA-2> for Alternate Tunnel Encapsulation Type
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o Length: > 4
o Tunnel-Type: The tunnel type is specified by a 2 byte value. This
specification defines the values from zero (0) to six (6) as given
below. The remaining values are reserved for future use.
* 0: CAPWAP. This refers to a CAPWAP data channel described in
[RFC5415] and [RFC5416].
* 1: L2TP. This refers to tunnel encapsulation described in
[RFC2661].
* 2: L2TPv3. This refers to tunnel encapsulation described in
[RFC3931].
* 3: IP-in-IP. This refers to tunnel encapsulation described in
[RFC2003].
* 4: PMIPv6-UDP. This refers to the UDP encapsulation mode
described in [RFC5844]. This encapsulation mode is the basic
encapsulation mode and does not include the TLV header
specified in section 7.2, of [RFC5845].
* 5: GRE. This refers to GRE tunnel encapsulation as described
in [RFC2784].
* 6: GTPv1-U. This refers to GTPv1 user plane mode as described
in [TS29281].
o Info Element: This field contains tunnel specific configuration
parameters to enable the WTP to setup the alternate tunnel. This
specification provides details for this elements for CAPWAP,
PMIPv6, and GRE. This specification reserves the tunnel type
values for the key tunnel types and defines the most common
message elements. It is anticipated that message elements for the
other protocols (like L2TPv3, etc.) will be defined in other
specifications in the future.
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication
The WTP MAY include the Alternate Tunnel Failure Indication message
in a WTP Event Request message to inform the AC about the status of
the Alternate Tunnel. For the case where WTP establishes data
tunnels with multiple ARs (e.g., under VNO scenario), the WTP needs
to notify the AC of which AR(s) are unavailable. The message element
contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WLAN ID | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication
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o Type: <IANA-3> for IEEE 802.11 WTP Alternate Tunnel Failure
Indication
o Length: > 4
o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value
MUST be between one (1) and 16.
o Status: An 8-bit boolean indicating whether the radio failure is
being reported or cleared. A value of zero is used to clear the
event, while a value of one is used to report the event.
o Reserved: MUST be set to a value of 0 and MUST be ignored by the
receiver.
o Access Router Information Element: IPv4 address or IPv6 address of
the Access Router that terminates the alternate tunnel. The
Access Router Information Elements allow the WTP to notify the AC
of which AR(s) are unavailable.
4. Alternate Tunnel Types
4.1. CAPWAP based Alternate Tunnel
If the CAPWAP encapsulation is selected by the AC and configured by
the AC to the WTP, the Info Element field defined in Section 3.2
SHOULD contain the following information:
o Access Router Information: IPv4 address or IPv6 address of the
Access Router for the alternate tunnel.
o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection
of data packets using DTLS. Use of data packet protection on a
WTP is not mandatory but determined by the associated AC policy
(This is consistent with the WTP behavior described in [RFC5415]).
o IEEE 802.11 Tagging Mode Policy: It is used to specify how the
CAPWAP data channel packet are to be tagged for QoS purposes (see
[RFC5416] for more details).
o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP
and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for
the CAPWAP data channels. When run over IPv6, the CAPWAP data
channel may use either UDP or UDP-lite.
The message element structure for CAPWAP encapsulation is shown in
Figure 9:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=0 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Tunnel DTLS Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. IEEE 802.11 Tagging Mode Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. CAPWAP Transport Protocol Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Alternate Tunnel Encapsulation - CAPWAP
4.2. PMIPv6 based Alternate Tunnel
Proxy Mobile IPv6 (PMIPv6) (defined in [RFC5213]) based user plane
can also be used as alternate tunnel encapsulation between the WTP
and the AR. In this scenario, a WTP acts as the Mobile Access
Gateway (MAG) function that manages the mobility-related signaling
for a station that is attached to the WTP IEEE 802.11 radio access.
The Local Mobility Anchor (LMA) function is at the AR. If PMIPv6 UDP
encapsulation is selected by the AC and configured by the AC to a
WTP, the Info Element field defined in Section 3.2 SHOULD contain the
following information:
o Access Router (acting as LMA) Information: IPv4 or IPv6 address
for the alternate tunnel endpoint.
The message element structure for PMIPv6 encapsulation is shown in
Figure 10:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=4 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Alternate Tunnel Encapsulation - PMIPv6
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4.3. GRE based Alternate Tunnel
Generic Routing Encapsulation (defined in [RFC2784]) mode based user
plane can also be used as alternate tunnel encapsulation between the
WTP and the AR. In this scenario, a WTP and the access router
represent the two end points of the GRE tunnel. If GRE encapsulation
is selected by the AC and configured by the AC to a WTP, the Info
Element field defined in Section 3.2 SHOULD contain the following
information:
o Access Router Information: IPv4 or IPv6 address for the alternate
tunnel endpoint.
o GRE Key Information: The Key field is intended to be used for
identifying an individual traffic flow within a tunnel [RFC2890].
The message element structure for GRE encapsulation is shown in
Figure 11:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=5 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Alternate Tunnel Encapsulation - GRE
5. Alternate Tunnel Information Elements
This section defines the various elements described in Section 4.1,
Section 4.2, and Section 4.3.
These information elements can only be included in the Alternate
Tunnel Encapsulations Type message element, and the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element as their sub-
elements.
5.1. Access Router Information Elements
The Access Router Information Elements allow the AC to notify a WTP
of which AR(s) are available for establishing a data tunnel. The AR
information may be IPv4 address, or IPv6 address.This information
element SHOULD be contained whatever the tunnel type is.
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If the Alternate Tunnel Encapsulations Type message element is sent
by the WTP to communicate the selected AR(s), this Access Router
Information Element SHOULD be contained.
The following are the Access Router Information Elements defined in
this specification. The AC can use one of them to notify the
destination information of the data tunnel to the WTP. The Elements
containing the AR IPv4 address MUST NOT be used if an IPv6 data
channel with IPv6 transport is used.
5.1.1. AR IPv4 List Element
This Element (see Figure 12) is used by the AC to configure a WTP
with the AR IPv4 address available for the WTP to establish the data
tunnel for user traffic.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AR IPv4 List Element
Type: 0
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
AR IPv4 Address: The IPv4 address of the AR. At least one IPv4
address SHALL be present. Multiple addresses may be provided for
load balancing or redundancy.
5.1.2. AR IPv6 List Element
This Element (see Figure 13) is used by the AC to configure a WTP
with the AR IPv6 address available for the WTP to establish the data
tunnel for user traffic.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv6 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: AR IPv6 List Element
Type: 1
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
AR IPv6 Address: The IPv6 address of the AR. At least one IPv6
address SHALL be present. Multiple addresses may be provided for
load balancing or redundancy.
5.2. Tunnel DTLS Policy Element
The AC distributes its DTLS usage policy for the CAPWAP data tunnel
between a WTP and the AR. There are multiple supported options,
represented by the bit field below as defined in AC Descriptor
message elements. The WTP MUST abide by one of the options for
tunneling user traffic with AR. The Tunnel DTLS Policy Element obeys
the definition in [RFC5415]. If, for reliability reasons, the AC has
provided more than one AR address in the Access Router Information
Element, the same Tunnel DTLS Policy (the last one in Figure 14) is
generally applied for all tunnels associated with those ARs.
Otherwise, Tunnel DTLS Policy MUST be bonded together with each of
the Access Router Information Elements, and the WTP will enforce the
independent tunnel DTLS policy for each tunnel with a specific AR.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tunnel DTLS Policy Element Type| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Tunnel DTLS Policy Element
Type: 2
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
Reserved: A set of reserved bits for future use. All implementations
complying with this protocol MUST set to zero any bits that are
reserved in the version of the protocol supported by that
implementation. Receivers MUST ignore all bits not defined for the
version of the protocol they support.
D: DTLS-Enabled Data Channel Supported (see [RFC5415]).
C: Clear Text Data Channel Supported (see [RFC5415]).
R: A reserved bit for future use (see [RFC5415]).
AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of
previously specified AR addresses.
The last element having no AR Information in Figure 14 is the default
tunnel DTLS policy, and provides options for any address not
previously mentioned. Therefore, the AR information field here is
optional. If all ARs share the same tunnel DTLS policy, in this
element, there will not be AR information field and its specific
tunnel DTLS policy.
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5.3. IEEE 802.11 Tagging Mode Policy Element
In 802.11 networks, IEEE 802.11 Tagging Mode Policy Element is used
to specify how the WTP applies the QoS tagging policy when receiving
the packets from stations on a particular radio. When the WTP sends
out the packet to data channel to the AR(s), the packets have to be
tagged for QoS purposes (see [RFC5416]).
The IEEE 802.11 Tagging Mode Policy abides the IEEE 802.11 WTP
Quality of Service defined in Section 6.22 of [RFC5416].
If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, the same IEEE
802.11 Tagging Mode Policy (the last one in Figure 15) is generally
applied for all tunnels associated with those ARs. Otherwise, IEEE
802.11 Tagging Mode Policy MUST be bonded together with each of the
Access Router Information Elements, and the WTP will enforce the
independent IEEE 802.11 Tagging Mode Policy for each tunnel with a
specific AR.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tagging Mode Policy Ele. Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: IEEE 802.11 Tagging Mode Policy Element
Type: 3
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
Reserved: A set of reserved bits for future use.
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P: When set, the WTP is to employ the 802.1p QoS mechanism (see
[RFC5416]).
Q: When the 'P' bit is set, the 'Q' bit is used by the AC to
communicate to the WTP how 802.1p QoS is to be enforced (see
[RFC5416]).
D: When set, the WTP is to employ the DSCP QoS mechanism (see
[RFC5416]).
O: When the 'D' bit is set, the 'O' bit is used by the AC to
communicate to the WTP how DSCP QoS is to be enforced on the outer
(tunneled) header (see [RFC5416]).
I: When the 'D' bit is set, the 'I' bit is used by the AC to
communicate to the WTP how DSCP QoS is to be enforced on the
station's packet (inner) header (see [RFC5416]).
AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of
previously specified AR addresses.
The last element having no AR Information in Figure 15 is the default
IEEE 802.11 Tagging Mode Policy, and provides options for any address
not previously mentioned. Therefore, the AR information field here
is optional. If all ARs share the same IEEE 802.11 Tagging Mode
Policy, in this element, there will not be AR information field and
its specific IEEE 802.11 Tagging Mode Policy.
5.4. CAPWAP Transport Protocol Element
The CAPWAP data tunnel supports both UDP and UDP-Lite (see
[RFC3828]). When run over IPv4, UDP is used for the CAPWAP data
channels. When run over IPv6, the CAPWAP data channel may use either
UDP or UDP-lite. The AC specifies and configures the WTP for which
transport protocol is to be used for the CAPWAP data tunnel.
The CAPWAP Transport Protocol Element abides the definition in
Section 4.6.14 of [RFC5415].
If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, the same CAPWAP
Transport Protocol (the last one in Figure 16) is generally applied
for all tunnels associated with those ARs. Otherwise, CAPWAP
Transport Protocol MUST be bonded together with each of the Access
Router Information Elements, and the WTP will enforce the independent
CAPWAP Transport Protocol for each tunnel with a specific AR.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: CAPWAP Transport Protocol Element
Type: 4
Length: 1
Transport: The transport to use for the CAPWAP Data channel. The
following enumerated values are supported:
1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the
CAPWAP Data channel. Note that this option MUST NOT be used if the
CAPWAP Control channel is being used over IPv4 and AR address is IPv4
contained in the AR Information Element.
2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data
channel.
AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of
previously specified AR addresses.
The last element having no AR Information in Figure 16 is the default
CAPWAP Transport Protocol, and provides options for any address not
previously mentioned. Therefore, the AR information field here is
optional. If all ARs share the same CAPWAP Transport Protocol, in
this element, there will not be AR information field and its specific
CAPWAP Transport Protocol.
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5.5. GRE Key Element
If a WTP receives the GRE Key Element in the Alternate Tunnel
Encapsulation message element for GRE selection, the WTP MUST insert
the GRE Key to the encapsulation packet (see [RFC2890]). An AR
acting as decapsulating tunnel endpoint identifies packets belonging
to a traffic flow based on the Key value.
The GRE Key Element field contains a four octet number defined in
[RFC2890].
If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, a GRE Key Element
MAY be bonded together with each of the Access Router Information
Elements, and the WTP will enforce the independent GRE Key for each
tunnel with a specific AR.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: GRE Key Element
Type: 5
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
GRE Key: The Key field contains a four octet number which is inserted
by the WTP according to [RFC2890].
AR Information: This means Access Router Information Element. In
this context, it SHOULD be restricted to a single address, and MUST
be the address of one of previously specified AR addresses.
Any address not explicitly mentioned here does not have a GRE key.
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5.6. IPv6 MTU Element
If AC has chosen a tunneling mechanism based on IPv6, it SHOULD
support the minimum IPv6 MTU requirements [RFC8200]. This issue is
described in [I-D.ietf-intarea-tunnels]. AC SHOULD inform the WTP
about the IPv6 MTU information in the "Tunnel Info Element" field.
If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, an IPv6 MTU Element
MAY be bonded together with each of the Access Router Information
Elements, and the WTP will enforce the independent IPv6 MTU for each
tunnel with a specific AR.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 MTU Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: IPv6 MTU Element
Type: 6
Length: This refers to the total length in octets of the element
excluding the Type and Length fields.
Minimum IPv6 MTU: The field contains a two octet number indicate the
minimum IPv6 MTU in the tunnel.
AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of
previously specified AR addresses.
6. IANA Considerations
This document requires the following IANA considerations.
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o <IANA-1>. This specification defines the Supported Alternate
Tunnel Encapsulations Type message element in Section 3.1. This
elements needs to be registered in the existing CAPWAP Message
Element Type registry, defined in [RFC5415]. The Type value for
this element needs to be between 1 and 1023 (see Section 15.7 in
[RFC5415]).
o <IANA-2>. This specification defines the Alternate Tunnel
Encapsulations Type message element in Section 3.2. This element
needs to be registered in the existing CAPWAP Message Element Type
registry, defined in [RFC5415]. The Type value for this element
needs to be between 1 and 1023.
o <IANA-3>. This specification defines the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element in
Section 3.3. This element needs to be registered in the existing
CAPWAP Message Element Type registry, defined in [RFC5415]. The
Type value for this element needs to be between 1024 and 2047.
o Alternate Tunnel-Types Registry: This specification defines the
Alternate Tunnel Encapsulations Type message element. This
element contains a field Tunnel-Type. The namespace for the field
is 16 bits (0-65535). This specification defines values, zero (0)
through six (6) and can be found in Section 3.2. Future
allocations of values in this name space are to be assigned by
IANA using the "Specification Required" policy. IANA needs to
create a registry called CAPWAP Alternate Tunnel-Types. The
registry format is given below.
Tunnel-Type Type Value Reference
CAPWAP 0 [RFC5415],[RFC5416]
L2TP 1 [RFC2661]
L2TPv3 2 [RFC3931]
IP-IP 3 [RFC2003]
PMIPv6-UDP 4 [RFC5844]
GRE 5 [RFC2784]
GTPv1-U 6 [3GPP TS 29.281]
o Alternate Tunnel Sub-elements Registry: This specification defines
the Alternate Tunnel Sub-elements. Currently, these information
elements can only be included in the Alternate Tunnel
Encapsulations Type message element, and the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element as their sub-
elements. These information elements contains a Type field. The
namespace for the field is 16 bits (0-65535). This specification
defines values, zero (0) through six (6) in Section 5. This
namespace is managed by IANA and assignments require an Expert
Review.
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Type Type Value
AR IPv4 List 0
AR IPv6 List 1
Tunnel DTLS Policy 2
IEEE 802.11 Tagging Mode Policy 3
CAPWAP Transport Protocol 4
GRE Key 5
IPv6 MTU 6
7. Security Considerations
This document introduces three new CAPWAP WTP message elements.
These elements are transported within CAPWAP Control messages as the
existing message elements. Therefore, this document does not
introduce any new security risks to the control plane compared to
[RFC5415] and [RFC5416]. In the data plane, if the encapsulation
type selected itself is not secured, it is suggested to protect the
tunnel by using known secure methods, such as IPSec.
8. Contributors
The authors would like to thank Andreas Schultz, Hong Liu, Yifan
Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey
Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and
Paul Kyzivat for their valuable comments.
9. References
9.1. Normative References
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996,
<https://www.rfc-editor.org/info/rfc2003>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
RFC 2661, DOI 10.17487/RFC2661, August 1999,
<https://www.rfc-editor.org/info/rfc2661>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<https://www.rfc-editor.org/info/rfc2784>.
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[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, DOI 10.17487/RFC2890, September 2000,
<https://www.rfc-editor.org/info/rfc2890>.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed.,
and G. Fairhurst, Ed., "The Lightweight User Datagram
Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July
2004, <https://www.rfc-editor.org/info/rfc3828>.
[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
"Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
RFC 3931, DOI 10.17487/RFC3931, March 2005,
<https://www.rfc-editor.org/info/rfc3931>.
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>.
[RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control and Provisioning of Wireless Access Points
(CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416,
DOI 10.17487/RFC5416, March 2009,
<https://www.rfc-editor.org/info/rfc5416>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References
[I-D.ietf-intarea-tunnels]
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-08 (work in
progress), January 2018.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<https://www.rfc-editor.org/info/rfc5213>.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010,
<https://www.rfc-editor.org/info/rfc5844>.
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[RFC5845] Muhanna, A., Khalil, M., Gundavelli, S., and K. Leung,
"Generic Routing Encapsulation (GRE) Key Option for Proxy
Mobile IPv6", RFC 5845, DOI 10.17487/RFC5845, June 2010,
<https://www.rfc-editor.org/info/rfc5845>.
[RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R.,
and S. Matsushima, "IEEE 802.11 Medium Access Control
(MAC) Profile for Control and Provisioning of Wireless
Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494,
April 2015, <https://www.rfc-editor.org/info/rfc7494>.
[TS29281] "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; General
Packet Radio System (GPRS) Tunnelling Protocol User Plane
(GTPv1-U)", 2016.
Authors' Addresses
Rong Zhang
China Telecom
No.109 Zhongshandadao avenue
Guangzhou 510630
China
Email: zhangr@gsta.com
Rajesh S. Pazhyannur
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: rpazhyan@cisco.com
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
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Zhen Cao
Huawei
Xinxi Rd. 3
Beijing 100085
China
Email: zhencao.ietf@gmail.com
Hui Deng
Huawei
Xinxi Rd. 3
Beijing 100085
China
Email: denghui02@gmail.com
Zongpeng Du
Huawei
No.156 Beiqing Rd. Z-park, HaiDian District
Beijing 100095
China
Email: duzongpeng@huawei.com
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